1.Purchase a light ale. This can also be done with a dark beer, but it'll require so much food coloring that it turns your teeth green when you drink it, and that's something most people would like to avoid.

2.Pour some of the beer into a glass or mug.

3.Place 4-6 drops of green food coloring in the beer. You can also experiment with adding blue food coloring, since the beer is already yellow and mixing that with blue makes green.

4.Pour the rest of the beer. The pouring action should mix in the food coloring, but stir lightly if needed. (Stirring too much can make the beer flat.)